| 摘要 |
An IC card has a peripheral circuit and a CPU. The peripheral circuit has a memory for storing data. The CPU controls various operations including an access operation of the memory. The IC card receives a supply voltage and a clock signal from an external unit. The IC card has a detector for detecting the supply voltage, a tester for testing the detected supply voltage, and an adjuster for adjusting the peripheral circuit according to a result of the voltage test. With these arrangements, the IC card stably operates on a wide range of supply voltages and is capable of coping with a fluctuation in the supply voltage. The tester may be incorporated in the CPU as one of functions thereof or may be realized by hardware that is arranged outside the CPU. The IC card and external unit constitute an IC card system.
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